The goals of the proposed work are to analyze the individual contribution and the cellular interactions of at least two bone cell types during hormonal stimulation. To facilitate such studies, we plan to continue our efforts to obtain highly purified populations of osteoclast-like and osteoblast-like cells which will be used as model systems. Bone active hormone elicit quite different responses in these two cell types, and it is hoped that by studying the changes induced in each cell type in a defined situation, we will be able to reconstruct the tissue response and the modulations operating on this response under various physiological conditions.